JPS6275318A - Displacement encoder - Google Patents

Abstract

PURPOSE:To obtain a high resolution with a small size while enabling the use of a code with a density much lower than in the demanded resolution, by shortening the pulse cycle used for counting while a code is arranged merely in the direction of displacement. CONSTITUTION:A signal processor 6 introduces outputs of detection elements 5a-5d and 5e-5h composing each of detection element groups 4a and 4b by the groups to individual code comparators 7 of code comparator units 8a and 8b having the comparator 7 four each as such between adjacent ones. Then, outputs of the comparators 8a and 8b are introduced to respective zero-cross angle-computing units 9a and 9b, which units 9a and 9b scan outputs of the detection elements 5a-5d and 5e-5h to detect two zero-cross angles contained in signals obtained. Two zero-cross angles in this group are added separately with an adder and then subtraction is done between the results. The subtraction values are counted with a counter 12 and outputted as absolute displacement signal, thereby enabling the finding of absolute displacement of a moving object.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an absolute displacement encoding device used when absolutely measuring angular displacement or linear displacement of an object.

[Technical background of the invention and its problems]

BACKGROUND ART Conventionally, as a means for absolutely measuring angular displacement or linear displacement of a movable object, a method using an absolute displacement encoding device such as a row encoder or a linear encoder has been known. These displacement encoding devices usually include a code body that moves with the displacement of a movable object, a code or pattern representing the displacement and absolute value is written on the code body, and this is detected by a detection element. It is configured. The means to improve the measurement resolution are to increase the density of the code written on the code body, to make the turns representing the absolute value finer, and to correspond to these, to increase the number of detection elements. The method of placement is adopted.

However, the conventional displacement encoding device configured as described above has the following problems. That is,
There is a limit to increasing the code density by reducing the size of the code, and installing a large number of detection elements that are relatively large in size compared to the code will inevitably increase the overall size. Since it is necessary to arrange the encoder in a direction perpendicular to the direction of displacement of the encoder, there is a problem in that the size of the encoder is significantly increased.

[Purpose of the invention]

The present invention has been made in view of these circumstances, and its purpose is to enable the use of codes with a density significantly lower than the required resolution, while still allowing a large number of detection elements to be used in the displacement direction. It is an object of the present invention to provide an absolute displacement encoding device that does not need to be installed in orthogonal directions, is small, and can provide high resolution.

[Summary of the invention]

According to the present invention, a code body that moves with the displacement of a movable object, at least two types of codes with different recording pitches written in the displacement direction on the code body, and a number of stages equal to the types of these codes. a detection element group each comprising a plurality of detection elements and detecting the code of a corresponding type;
There is provided a displacement encoding device comprising means for detecting a phase difference between signals obtained by scanning the outputs of the detection elements constituting the detection element group.

[Effects of the Invention] With the above configuration, the absolute displacement can be determined by electrically counting the phase difference between the signals obtained by scanning the outputs of the detection elements constituting each detection element group. be able to.

At this time, resolution can be improved by shortening the pulse period used for counting. Furthermore, the codes may simply be arranged in the displacement direction, and do not need to be absolute patterns finely spread on a plane. Therefore, it is not necessary to arrange the detection element in a direction perpendicular to the displacement direction. Therefore, it is possible to downsize the entire device.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows an example in which a displacement encoding device according to an embodiment of the present invention is applied to a rotary encoder.

In the figure, la and lb are disc-shaped code bodies arranged coaxially, and these code bodies 1a and l
b is connected via shaft 2 to a movable object (not shown) whose absolute angular displacement is to be measured. Codes 3a are recorded on the periphery of the code body 1a at an angular pitch of 2θa. In this embodiment, magnetic codes magnetized in the axial direction of the shaft 2 are used as the codes 3a, and each code 3a is magnetized so that adjacent codes have opposite polarities.

A detection element group 4a for detecting the code 3a is located at a position opposite to the part of the code body 1a where the code 3a is provided.
is fixed on a substrate (not shown) in a non-contact state with the code body 1a. The detection element group 4a is sensitive to the lines of magnetic force coming out from each symbol 3a.

For example, four magnetoresistive elements (hereinafter referred to as MR elements) are used.

) are arranged in the rotational direction of the code body "a" at a pitch of θa/2.

On the other hand, the code 3b is also attached to the periphery of the code body 1b.
The angular pitch 2θb is recorded which is different from the arrangement angular pitch of a. This code 3b is composed of magnetic codes that are magnetized in the axial direction of the shaft 2 in the same way as the code 3a, and each code 3b is magnetized so that adjacent codes have opposite polarities. ing. At a position opposite to the portion of the code body 1b where the code 3b is provided, a detection element group 4b for detecting the code 3b is fixed on a substrate (not shown) in a non-contact state with the code body 1b. . The detection element group 4b is also constructed by arranging detection elements 5e to 5h, which are four MR elements, at a pitch of θb/2 in the rotational direction of the encoder 1b.

Thus, the outputs of the detection elements 5a to 5h constituting the detection element groups 4a and 4b are introduced into the signal processing device 6. The signal processing device 6, as shown in FIG.
The outputs of the signals d and 5e to 5h are introduced into the code comparators of adjacent code comparators 8a and 8b each having four code comparators 7. The outputs of the sign comparators 8a and 8b are introduced into zero-cross angle calculation devices 9a and 9b, respectively. These zero cross angle calculation devices 9a, 9b are connected to each of the detection elements 5a to 5d and 5.
Two zero-crossing angles present in the signals obtained by scanning the outputs of e to 5h are detected. The two zero cross angles θal, θa2 and θbl, θb2 calculated by these zero cross angle calculating devices 9a and 9b are as follows:
After being added by adders 10a and 10b, respectively, they are subtracted by a subtracter 11. Then, this subtracted value is calculated by the counter 12.
This counted value is output as an absolute displacement signal X.

Next, the operation of the apparatus configured as described above will be explained.

For simplicity of explanation, code body 1a.

It is assumed that the symbols 3a and 3b written on 1b are observed in the form of a triangular wave, and the angular pitch is set so that the respective symbols 3a and 3b satisfy a mutually prime relationship. Also, codes 3a and 3b written in code bodies 1a and lb
It is assumed that when the phase of the angular displacement is zero (θ-〇) as shown in FIG. 3, there is a complete bush. In this way, the position of zero angular displacement is set as the base line, and at this base line position, the detecting elements 5a to 5d and 5 constituting the detecting element groups 4a and 4b are
If the outputs of e to 5h are scanned at equal intervals, the signals shown in FIG. 4 are obtained. There is no phase difference in electrical angle between the signal obtained from the detection element group 4a side and the signal obtained from the detection element R4b side.

When the movable object undergoes angular displacement, the code bodies 1a, lb and the detection element group 4
When the relative relationship with a and 4b reaches the position θ-θX in FIG. 3, the detection element group 4a.

The signals obtained by scanning the outputs of the detection elements 5a to 5d and 5e to 5h of 4b exhibit the appearance shown in FIG. 5, and an electrical angle phase difference Δθ occurs between the two signals. Since the numbers of codes provided in the code bodies 1a and lb have a mutually prime relationship, the code bodies 1a.

During one rotation of 1b, Δθ changes from zero to 2π. Further, when each code number is not prime but has a common divisor, in the angular range obtained by dividing one rotation angle of the code bodies 1a and lb by the greatest common divisor.

Δθ changes from zero to 21. The device of the present invention electrically detects this phase difference. In other words, the signals obtained in a scanning manner from the detection element groups 4a and 4b have a form that oscillates in positive and negative directions around zero.
Two zero-crossing angles θal for one code pitch,
θb2, θb1, and θb2 exist. The sign comparing devices 8a and 8b are used to determine in which range the zero crossing point exists. The zero-crossing angle is calculated by the zero-crossing calculation devices 9a and 9b using the output values of the two detection elements sandwiching the zero-crossing point. These two zero cross angles θa1. θb2 and θbl, θ
b2 are added by adders 10a and 10b, respectively. Outputs θaO and θb of the adders 10a and 10b
O can be regarded as the phase angle of the code bodies 1a and lb.

These two phase angles θaO and θbO have different values during one rotation of the code bodies 1a and lb when the two types of codes are prime numbers. And these two phase angles θaO
and θbO are subtracted by a subtracter 11, and the value thereof is counted by a counter 12.

Therefore, from the output X of the counter 12, the code bodies la, l
b, that is, the absolute angular displacement of the movable object.

In this case, the absolute angular displacement can be measured without increasing the density of the symbols 3a and 3b and without arranging a large number of detection elements in the direction orthogonal to the displacement direction, so the overall size of the device can be reduced. I can do that. Further, by shortening the clock pulse period of the counter 12, the resolution can also be improved, and the above-mentioned effects can be achieved after all.

Note that the present invention is not limited to the embodiments described above, and can be modified in various ways. That is, in the embodiments described above, a magnetic code is used as the code and an MR element is used as the detection element.

It can also be applied to cases where encoding and code detection methods using other physical quantities such as optical methods are used. In addition, ``Two consecutive examples are 1
Although this is an example in which the present invention is applied to measuring absolute angular displacement, it goes without saying that the present invention can also be applied to measuring absolute linear displacement. Also, in the 100 million actual examples mentioned above, are the same number of code bodies as types of codes used?

Each code string may be arranged in two columns on one code body.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a displacement encoding device according to an embodiment of the present invention (1M diagram, FIG. 2 is a block diagram of a processing device in the device, and FIGS. 3 to 5 explain the operation of the device. la, 1b...code body, i...axis, 3a, 3b, -1 code, 4a, 4b...detection element group, 5a-5h...detection element, 6...・Signal processing device. Applicant's representative Patent attorney Takehiko Suzue Figure 1 4a 4b Figure 2 Figure 3

Claims (1)

[Claims] A code body that moves in accordance with the displacement of a movable object, at least two types of codes with different recording pitches written in the displacement direction on the code body, and a plurality of detection elements each provided in the same number as the types of these codes. a detection element group configured to detect the corresponding type of code, and means for detecting a phase difference between signals obtained by scanning the outputs of the detection elements constituting the detection element group. A displacement encoding device characterized by: